Adaptive Reference Resistance for Accurate Measurement of Resistive Sensors With Microcontroller

Abstract

This research proposes a method to enhance the accuracy of resistance measurements for Resistive Sensors (${R} _{x}$) using a voltage divider and Anderson current loop circuits connected to the analog-to-digital converter (ADC) of a microcontroller. Traditional circuits use a fixed reference resistor (FRR) (${R} _{\text {ref}}$), which causes significant errors when the sensor’s voltage drop differs greatly from the reference resistor. In order to address this, an adaptive reference resistor (ADRR) using a digital potentiometer (DPOT) is introduced. The voltage drop across the resistive sensor is used to determine the control code for the DPOT. This adjusts the reference resistance to be close to the sensor resistance. The introduction of the Tuning Factor (k) for calibrating the measurement system, moreover, significantly reduces errors. The experiment used an MCP41010 DPOT with 256 steps, whose resistance was measured and calibrated by a factor,k. Known resistances were used for accuracy testing within the range of 100–$9960~\Omega $. According to the results, setting the reference resistance interval to$100~\Omega $led to an error of less than 0.45% for the voltage divider circuit across the measurement range. Meanwhile, the series circuit based on the Anderson current loop demonstrated an error of less than 0.35%.